1. Field of Invention
The present invention relates to an active roll control system for a vehicle. More particularly, the present invention relates to an active roll control system (ARCS) which can actively control roll of a stabilizer bar connected to a pair of upper arms mounted respectively at both sides of a vehicle body through stabilizer links.
2. Description of Related Art
Generally, a suspension system of a vehicle connects an axle to a vehicle body so as to control vibration or impact transmitted from a road to the axle when driving not to be directly transmitted to the vehicle body. Accordingly, the suspension system of a vehicle prevents the vehicle body and freight from being damaged and improves ride comfort.
Such a suspension system, as shown in FIG. 1, includes a chassis spring 101 relieving impact from the road, a shock absorber 103 reducing free vibration of the chassis spring 101 and improving the ride comfort, and a stabilizer bar 105 suppressing roll of a vehicle (it means that a vehicle inclines with reference to a length direction of the vehicle body).
Herein, the stabilizer bar 105 includes a straight portion and both ends. Both sides of the straight portion are mounted at the vehicle body 107, and the both ends are mounted at a lower arm 109 or a strut bar that is a suspension arm through the stabilizer link 113. Therefore, in a case that left and right wheels 111 move to the same direction (upward direction or downward direction), the stabilizer bar 105 does not work. On the contrary, in a case that the left and right wheels 111 move to the opposite direction (one moves upwardly and the other moves downwardly), the stabilizer bar 105 is twisted and suppresses the roll of the vehicle body 107 by torsional restoring force.
That is, when the vehicle body 107 inclines toward a turning axis by the centrifugal force in a case of turning or heights of the left and right wheels is different from each other by bump or rebound of the vehicle, the stabilizer bar 105 is twisted and stabilizes position of the vehicle body by torsional restoring force.
Since a conventional stabilizer bar 105, however, has a constant roll rigidity, it is insufficient to secure turning stability under various driving conditions by means of torsional elastic force of the stabilizer bar 105 only.
Recently, an active roll control system having an actuator consisting of a hydraulic pressure cylinder 115 and connected to an end of the stabilizer bar 105 so as to control roll actively has been developed as shown in FIG. 2.
The active roll control system uses the hydraulic pressure cylinder 115 instead of the stabilizer link 113 connecting the lower arm 109 and the end of the stabilizer bar 105 so as to change a connecting length between the end of the stabilizer bar 105 and the lower arm 109. Therefore, roll rigidity of the stabilizer bar 105 is changed.
That is, a lower end of the hydraulic pressure cylinder 115 is connected to the lower arm 109 and a front end of a piston rod 117 of the hydraulic pressure cylinder 115 is connected to the end of the stabilizer bar 105 through a ball joint 119 according to the active roll control system.
According to the active roll control system, an electronic control unit (ECU) controls a hydraulic pressure system including valves, hydraulic pressure pumps, and so on based on signals output from an acceleration sensor, a height sensor, and a steering sensor of the vehicle so as to enhance roll of the vehicle.
The lower end of the hydraulic pressure cylinder 115, however, should be assembled through a separate bracket 121 having a lower end protruded under the lower arm 109 so as to secure an operation stroke of the hydraulic pressure cylinder 115 (i.e., actuator) to the maximum. Such a layout can be designed but productivity may be deteriorated.
Since the hydraulic pressure cylinder 115 is used as the actuator, components for generating and delivering hydraulic pressure (i.e., hydraulic pressure pumps, hydraulic pressure lines, valves and so on) should be necessary.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.